The present invention relates to a control apparatus of a gas turbine combustor and, more particularly, to a control apparatus of a gas turbine combustor for effecting a stable combustion with limited NOx emission through a control of a fuel flow rate and a control of an air flow rate of an intake air to be mixed with the fuel.
A two-stage type low NOx gas turbine combustor which effects combustion with low NOx emission and suppressed uncombustion products such as CO, HC is disclosed in JP A 60-91141. The gas turbine combustor comprises a head combustion chamber for effecting a first stage combustion with first stage fuel and a first stage combustion air introduced therein and a main combustion chamber at a downstream side of the head combustion chamber for effecting combustion with a mixture of second stage fuel and a second stage combustion air. The combustor is characterized by the provision of means for changing a flow rate of the second stage combustion air. The combustor controls a flow rate of the second stage combustion air according to a gas turbine output to be surplus air. Therefore, if the gas turbine output is constant, a flow rate of the second stage combustion air becomes constant and a fuel/air ratio also is constant. In this conventional combustor, the flow rate of the second stage combustion air is set, in advance, as a function of a gas turbine output, and the flow rate is increased according to the function as an increase of the gas turbine output.
In this conventional combustor, a change in intake air conditions is not taken into consideration, and there is a problem that since the same air flow rate is taken at the same gas turbine output, the combustion temperature lowers when the absolute humidity of the intake air increases, and the combustion condition shifts into an unstable combustion region. Further, it has a problem that when the absolute humidity of the intake air decreases, a generation amount of NOx increases beyond a limit value.
Further, JP A 2-33419 discloses a gas turbine combustor which is provided with a detector for detecting the humidity of combustion air and controlled to shift a control setting according to the detected humidity, in order to effect a stable combustion with a low NOx emission over the year without being influenced by atmosphere humidity conditions. The prior art JP A 2-33419 does not clearly disclose a concrete method of control on the basis of detection of the intake air humidity, but discloses, in the embodiment, that a humidity sensor 18 for detecting the humidity of air introduced into the combustor is provided on the upstream side of a compressor, and the signal is inputted into a valve controller 17, whereby a control of valve opening is shifted according to the humidity as shown in FIG. 4 (FIG. 4 is a prior art, therefore it may be FIG. 2).